Sound signal processing systems are well-known in the art that have a plurality of microphones and receives audio signals input via the microphones. As is prone to be with this type of the sound signal processing systems, when input through the microphones, the same sound appears different in power that indicates magnitude of the sound represented by an audio signal received through each of the microphones (i.e., power of the audio signal) because of dissimilarities inherent to the microphones, different degrees of deterioration over time, divergent types of signal transmission system (e.g., wiring), and the like.
Thus, this type of the sound signal processing systems employ a signal correction apparatus that predetermines, for each frequency, a correction coefficient used for approximating the power of the audio signal received via each of the microphones to the reference power and then uses the predetermined correction coefficient to correct the power of the audio signal received via each of the microphone (e.g., see Patent Document 1 listed below).
Such a signal correction apparatus receives the audio signal input via a certain one of the microphones and computes the power of the received audio signal at every frequency. Then, the signal correction apparatus computes, for each frequency, a rate of the reference power used as a criteria (e.g., an average of all the values of the power obtained for each of the microphones) to the computation result for the power of the audio signal so as to determine in advance the correction coefficient according as the computed rate. After that, the signal correction apparatus corrects the power of the received audio signal based upon the predetermined correction coefficient. In this manner, the received audio signal can have its power approximated to the reference power at each frequency.